Twenty-eight. That's how many times we dropped the Motorola Moto Z2 Force to test the claims of its shatter-resistant screen. ShatterShield, the name for Motorola's hardcoat layer, promises that the display won't shatter or crack when dropped at a height of 4 or 5 feet.

And it didn't, even after smacking it face-down nearly 30 times total against wood, plexiglass, ceramic, concrete and rock. That doesn't mean the screen emerged scratch-free. In fact, the surface was festooned with scratches, gouges and pitting, especially after hitting hard onto concrete and skidding and tumbling over rocks.

Since the outermost surface isn't glass, the screen is still completely usable after dinging it up; you won't slice your finger the way you can on an especially bad glass screen crack.That said, some gouges were so deep, the peeled-back parts of the top layer do rough up the surface and would get in the way. Hopefully most people won't be as butterfingered as we intentionally were, but the outcome could happen.

Motorola advertises that ShatterShield has a four-year warranty, and a screen replacement costs $30 on the Z Force and Droid Turbo 2, two other phones that also used the material.

Here's what we found in our tests.

Wood

We wanted to establish a baseline, so we started by dropping the Moto Z2 Force face-down on a wooden floor in our office, from 3, 4 and 5 feet (we repeated some tests). Along the way, we noticed some subtle damage along the edges. The material looked like it was starting to ever-so slightly pull away from the phone's aluminum frame, but it didn't completely separate.

Ceramic

Stop pretending you don't take your phone into the bathroom; we know you do. And we also know that the ceramic tile flooring in many bathrooms is particularly device-slaying. We knocked the Z2 Force off the bathroom sink a few times, 3 feet high, and off a paper towel dispenser twice, about 5 feet. It survived both scenarios.

Concrete

Holding a phone in one hand while glamming it up for the camera can be awkward, and when grips are awkward, phones can take a tumble. We fumbled the Z2 Force at different selfie heights onto the sidewalk and the hard plaza of CNET's San Francisco headquarters. On the ninth drop (out of all 28), the screen got its first major ding, a scrape on the phone's top right corner that peeled away a portion of the ShatterShield topcoat. No other scrapes in subsequent drops.

Plexiglass

We set up a layer of hard plexiglass between two boxes and dropped the phone face-down on that several times. This was mostly done to set up a video shot. After the pummeling on concrete, the Z2 Force escaped this relatively mild surface casualty-free.

Rock

I love hiking, and taking photos of outdoor walks with my phone. So our video team traipsed down to the coast to simulate some tumbles onto the rugged sandstone and rocks at one of San Francisco's harshest bits of beach. We dropped the Z2 Force 10 times in four different spots, purposely saving these most punishing drops for last. Punishing, it was. The loose rocks immediately scratched, scraped and scuffed the Z2 Force's display -- but the screen was, for the most part, usable until the damage really added up. In real life, you'd probably only drop it in this environment once.

Drop 28: Bonus round

This was a drop test, not a torture test, so we didn't go out of our way to see what it would take to crack the screen. (So no nails, hammers, pickaxes, etc.) But we did want to know what would happen if the phone fell from a greater height, because in the real world, phones fall from a variety of heights, not all of them 5 feet or under.

We dropped the Z2 Force from a rocky outcropping about 30 feet tall, watching it tumble over more rock to the hard-pack dirt below. It picked up more dings, but the screen didn't crack or shatter.

The take-away

ShatterShield does what it says. After a beating, the Moto Z2 Force was absolutely roughed up, but the screen upheld Moto's promise.

Is it worth its high $730 price? That's a tougher question to answer. It's a great phone right now, but we're on the cusp of seeing the keystone competitors in the phone market: The Galaxy Note 8, the next iPhone (or iPhones), the Google Pixel 2 and a new LG flagship are all expected to be unveiled before the end of October. While the Z2 Force is great now, it may not be so high on our list in a couple months.

If you buy the Moto Z2 Force because of its screen protection alone, we'd instead recommend buying a case and glass screen protector for the cheaper $400, very good Moto Z2 Play, and put the savings to good use.